1. Field of the Invention
The present invention relates to an image recognition technology to detect a specific pattern in the image.
2. Description of the Related Art
Color copying machines have been improved in both function and performance in recent years. Against this backdrop, methods to prevent counterfeiting of bills and securities are being studied on an ongoing basis. One of such methods includes the following procedure: A specific pattern is included in the graphics of the bill or other security, such that when the bill or other security is scanned by a color copying machine, and the image obtained via the scanning is analyzed, if the specific pattern is detected in the image, normal image formation is prohibited.
Most of the image data from input devices is color images, which contain large amounts of information, and input/output apparatuses offer increasingly faster speed and higher resolution. Nonetheless, real-time image processing is demanded for the purpose of counterfeit prevention. Therefore, a procedure for high-speed, high-precision image recognition to detect a specific pattern must be developed.
As a conventional pattern recognition method that is performed in order to detect the position of an object or to recognize the configuration thereof, a method is known in which pattern matching is performed while shifting is carried out from one pixel to another. In this pattern matching, the data for each pixel of the image incorporated into the image processing apparatus is stored in the image memory as either binary data, i.e., monochrome data, or multi-level data, and the data thus stored is checked against the data for each pixel of a reference pattern that is stored in the memory in advance on a one-to-one basis.
In this pattern matching technology, data for a reference pattern used for the recognition of the specific pattern is prepared in advance, and the data for each pixel of the image is checked against the data for each pixel of the reference pattern on a pixel-by-pixel basis. Therefore, data for a reference pattern must be prepared in advance. For example, where images of circles of different sizes are used as the specific patterns, reference patterns must be prepared that will match the number of the different sizes. Furthermore, if the program is reverse-engineered, the reference pattern is easy to find, which means such a method is not safe.